According to most authentic traditions in collections of both Sunni and Shia, Ahlulbait (People of the House) of the Prophet are one of the two most precious Symbols of Islam after the departure of the Prophet (S.A.A.W.W). There are numerous traditions in the collection of both schools that the Prophet (S.A.A.W.W) has reminded us to stick to these two weighty things (al-Thaqalayn), namely Quran and Ahlulbait , in order not to go astray after him.
The Messenger of Allah also informed us that these two weights are non-separable and are with each other till the day of Judgement. This requires us that for understanding the interpretation of Quran and the Sunnah of the Prophet (S.A.A.W.W) we should refer to those who are attached to it, namely Ahlulbait .
Knowing exactly who Ahlulbait are, thus becomes a very vital matter when one considers the above tradition of the Prophet (S.A.A.W.W) as well as many other traditions which unequivocally state that adherence to Ahlulbait is the only way of salvation. This clearly implies that the one who follows a wrong set of Ahlulbait (!!), will be led astray.